OSPF Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)
updated by
- rfc-6001 — Generalized MPLS (GMPLS) Protocol Extensions for Multi-Layer and Multi-Region Networks (MLN/MRN)
- rfc-6002 — Generalized MPLS (GMPLS) Data Channel Switching Capable (DCSC) and Channel Set Label Extensions
- rfc-7074 — Revised Definition of the GMPLS Switching Capability and Type Fields
updates
- rfc-3630 — Traffic Engineering (TE) Extensions to OSPF Version 2
Extracted elements (22)
Link Local/Remote Identifiers are carried in a link-local Opaque LSA (type 9) rather than area-scope LSAs because this information only needs to be exchanged over the specific interface in question, making link-local flooding the appropriate scope.
Maximum LSP Bandwidth is encoded in bytes per second (not bits per second) using IEEE 754 floating-point to accommodate the wide range of bandwidth values across packet, TDM, lambda, and fiber switching layers in GMPLS.
Neighbors of a restarting node should continue to advertise the actual unreserved bandwidth on TE links toward that node; regular or TE graceful restart need not be aborted if a TE LSA or TE topology changes.
The document strongly recommends that IANA grant the specific sub-TLV type values suggested (11, 14, 15, 16) because interoperable implementations already exist using these values.
During graceful restart, before it can determine unreserved resources, the restarting node SHOULD originate TE LSAs with 0 unreserved bandwidth; for LSC or FSC links, also with 0 Max LSP Bandwidth. This discourages new LSP establishment through the restarting router.
Sub-TLVs of the TE Link TLV in the range 10–32767 must be assigned by Expert Review and registered with IANA, per RFC 3630.
The 2-octet padding in the PSC Switching Capability-specific information field SHOULD be set to zero by the sender and SHOULD be ignored by the receiver.
The 3-octet padding in the TDM Switching Capability-specific information field SHOULD be set to zero by the sender and SHOULD be ignored by the receiver.
The three reserved octets in the Link Protection Type sub-TLV SHOULD be set to zero by the sender and SHOULD be ignored by the receiver.
A TE Link Local LSA is an OSPF Opaque LSA of type 9 (link-local flooding scope) with Opaque Type 1 and Opaque ID 0, used to exchange per-interface TE information (such as Link Local Identifier) only over that interface.
Four new sub-TLVs are added to the OSPF TE Link TLV: Link Local/Remote Identifiers (type 11), Link Protection Type (type 14), Interface Switching Capability Descriptor (type 15), and Shared Risk Link Group (type 16).
The Interface Switching Capability Descriptor sub-TLV may occur more than once within the Link TLV to support interfaces with multiple switching capability descriptors. By contrast, the Link Protection Type and SRLG sub-TLVs may each occur at most once.
The Link Local Identifier TLV within the TE Link Local LSA has Top Level Type 4; the only defined sub-TLV has Type 1, Length 4, and a 32-bit Link Local Identifier value.
The Switching Capability field in the Interface Switching Capability Descriptor encodes interface switching types: PSC-1 through PSC-4 (values 1–4), L2SC (51), TDM (100), LSC (150), and FSC (200). L2SC and LSC have no Switching Capability-specific information field.
Four new sub-TLV types for the OSPF TE Link TLV are registered with IANA: type 11 (Link Local/Remote Identifiers), type 14 (Link Protection Type), type 15 (Interface Switching Capability Descriptor), and type 16 (Shared Risk Link Group). A new Top Level Type for the Link Local TLV is also allocated from the Standards Action space.
GMPLS TE LSAs (Opaque LSAs) are not used for SPF or normal IP routing, so tampering has no direct effect on IP routing. However, tampering may affect the underlying transport (optical/SONET-SDH) network. Mechanisms such as OSPF with Digital Signatures (RFC 2154) should be used to secure the information.
For PSC-1/2/3/4 switching capability, the Switching Capability-specific information includes a 4-octet Minimum LSP Bandwidth (IEEE float, bytes/sec), a 2-octet Interface MTU, and 2 octets of padding for 32-bit alignment.
For TDM switching capability, the Switching Capability-specific information includes a 4-octet Minimum LSP Bandwidth (IEEE float), a 1-octet indication of Standard (0) or Arbitrary (1) SONET/SDH support, and 3 octets of padding.
Interface Switching Capability Descriptor sub-TLV (type 15) encodes a 1-octet Switching Cap field, a 1-octet Encoding field, 2 reserved octets, eight 4-octet IEEE floating-point Max LSP Bandwidth fields (priorities 0–7 in bytes/second), and variable Switching Capability-specific information.
Link Local/Remote Identifiers sub-TLV (type 11, length 8 octets) carries a 4-octet Link Local Identifier followed by a 4-octet Link Remote Identifier. If the Link Remote Identifier is unknown, it is set to 0.
Link Protection Type sub-TLV (type 14, length 4 octets) encodes protection capabilities in the first octet as a bit vector (0x01=Extra Traffic, 0x02=Unprotected, 0x04=Shared, 0x08=Dedicated 1:1, 0x10=Dedicated 1+1, 0x20=Enhanced). The remaining 3 octets are reserved.
Shared Risk Link Group (SRLG) sub-TLV (type 16) carries an unordered list of 32-bit SRLG values as the value field; length equals the total list length in octets.